This invention relates to the preparation of saturated aliphatic diamines by the catalytic hydrogenation of unsaturated aliphatic dinitriles. It further relates to a catalyst composition effective in the hydrogenation of unsaturated aliphatic dinitriles to saturated aliphatic diamines.
In general, various processes for the catalytic hydrogenation of unsaturated aliphatic dinitriles to saturated aliphatic diamines are known in the art. Supported Group VIII metal catalysts such as cobalt, nickel, ruthenium, rhodium or palladium have been employed as catalysts for hydrogenating various feedstocks in these processes. The hydrogenation of branched-chain unsaturated aliphatic dinitriles in the presence of supported rhodium catalysts is disclosed in U.S. Pat. No. 3,880,928. It has been found that these Group VIII metal hydrogenation catalysts differ in their effectiveness and efficiency in hydrogenating unsaturated aliphatic dinitriles of the formula ##STR1## wherein each R is an alkylene or an alkylidene radical and R' is an alkyl radical. For example, some supported metal hydrogenation catalysts have insufficient physical stability or low catalytic activity under conditions present during the dehydrogenation reaction.
It is an object of this invention to provide a method for the hydrogenation of unsaturated aliphatic dinitriles. It is a further object to provide a supported metal catalyst for the hydrogenation of unsaturated aliphatic dinitriles which is both stable under hydrogenation reaction conditions and has high catalytic activity. It is a further object to provide a method of preparing a stable supported rhodium hydrogenation catalyst.